Brain Circuits

Each neurodegenerative disease is defined by selectively vulnerable neurons, regions, networks, and functions, as well as genetic risk factors. In the past decade, new network-sensitive neuroimaging methods have made it possible to test the notion of network-based degeneration in living humans. This chapter focuses on two common causes of dementia, Alzheimer’s disease (AD) and frontotemporal dementia (FTD), but uses these diseases to illustrate class-wide neurodegeneration principles whenever possible. It first introduces two key concepts of neurodegenerative disease selective vulnerability: onset and progression. In parallel, it addresses two distinct but related observations about neurodegenerative disease: clinico-anatomical convergence and phenotypic heterogeneity. It then examines disease onset and models of progression in more detail, based on available neuroimaging evidence. Finally, it touches on the most important frontiers in the field of network-based neurodegeneration.